II have two of these similar watch cases and bezels and three different movements and case backs. The subject watch question is the first photo - a 1948 dated case with a 1947 dated 15J 10BC movement. In the second photo I show both my complete watches (L: 1948 Brewster; R: 1960 Unknown; Middle: 1946 dated 15J 10BC with a case back that starts with a "5" for 1945. The case back fits the Brewster bezel. The third watch on the right is a 1959 (L9) dated case with a 1960 (M0) date 17J 11AF movement. The third photo shows the this subject watch in comparison to the 1960 dated 11AF watch. The bezel is only slightly different in the lugs and in the crown area - otherwise they are exactly the same size and take the same crystal. I could not find any similar bezel and case for 1959-60 so I'll post it as an Unknown...however, I did want to point out the similarities between the two watches.
Lugs are thicker on the watch on the left and are beveled. Two different watches here. Bezel on right is not same as bezel on left. Where the stem comes out of the bezel you have a slight nub where the crownrests on it. The hands are not Brewester and I don't personally recal a dial with the 17 jewels printed, on the 23j yes but not a 17 IMO. The first watch is a Brewster IMO and gets my 3 ticks.
Just Thought I would add something to this thread for those unsuspecting people looking for crystals. In the original description above it says the Brewster (1940s) takes the same crystal as the Unknown S.V.P VI model from the 1950s. I have found this incorrect. The Earlier Brewster watch actually takes a CMY312-18. The later SVP VI takes a CMW445. I tried fitting the CMW445 to my Brewster based on the above info and it falls just shy and doesn't quite fit the corners. The CMY312-18 Fits perfectly but is too large for my SVP VI unknown model.
Hope this helps somone out there before they purchase the wrong crystal like me.